ASYNC GETOUTQUECOUNT

Returns the number of characters in the transmit queue.

Category

IOCTL_ASYNC (01h)

Function

ASYNC_GETOUTQUECOUNT (69h)

Parameter Packet Format

None. Packet pointer must be NULL.

Data Packet Format

┌──────────────────────────────────────────────────────┐
│Field                          Length     C Datatype  │
├──────────────────────────────────────────────────────┤
│Number of Characters Queued    WORD       USHORT      │
├──────────────────────────────────────────────────────┤
│Size of Transmit Queue         WORD       USHORT      │
└──────────────────────────────────────────────────────┘

Related C Data Structure

The RXQUEUE data structure can be used by C programmers.

To include this data structure in your file, make sure INCL_DOSDEVIOCTL is defined before you include OS2.H.

Number of Characters Queued

Binary integer with the number of characters ready to be transmitted in the physical device driver transmit queue. This is a memory buffer between the memory pointed to by the WRITE request packet and the transmit hardware for this COM device. If the transmit queue is empty, the application cannot assume that all Write requests have completed or that no Write requests are outstanding.

Note

:The behavior of data movement between the Write request and the transmit queue can change with each release of the physical device driver. Applications should not be dependent on this information.

Size of Transmit Queue

Binary integer with the size of the physical device driver transmit queue. Applications should be independent of the transmit queue size (fixed or not fixed). The information in this field allows the application to get the size of the transmit queue, but is subject to change.

Returns

If the call is made with an invalid Parameter Packet value, a general failure error is reported and valid information is not returned in the Data Packet.

Remarks

If a general failure error is not returned, the physical device driver returns the information.